D.gnu - FYI: GNAT Front-end written in Ada

The GNAT (Ada 95 compiler) front end was (still?) written in Ada. It tracked
separately from GCC releases for many years (which users didn't particularly
like) but it recently joined the general release. Cross compilers are
available with GNAT. You may want to check the history of this open source
project to get some ideas for D.gnu.
Mark